1. Field of the Invention
The present invention relates to a fan having holding arms to be attached to a heat sink, and a cooling apparatus in which a heat sink and the fan attached to the heat sink. More particularly, the present invention relates to a molding die assembly for molding a frame member as a portion of the fan, and a method of manufacturing the frame member by using the molding die assembly.
2. Description of the Related Art
A typical CPU or MPU installed in a computer generates much heat during operation. The CPU or MPU has to be cooled so that its temperature is kept in a predetermined range. A cooling apparatus in which a fan is attached to a heat sink is used for cooling the CPU or MPU. The fan of this cooling apparatus has holding arms for attaching the fan to a heat sink.
In an exemplary fan of a cooling apparatus, holding arms of a fan housing are provided so as to face each other in a predetermined direction perpendicular to an axial direction of the fan, and extend parallel to the axial direction of the fan. Each holding arm has a catch projection at its tip. The catch projection is provided on an inner surface of the holding arm in the above predetermined direction for securing the fan to a corresponding portion of the heat sink from outside.
In this case, however, the catch projection of the holding arm catches the heat sink with an inward force in the predetermined direction at a position axially outside the fan housing. Thus, stability of attachment of the fan to the heat sink is not always sufficient.
Moreover, formation of the fan housing having the holding arm with the aforementioned catch projection by molding using a molding die assembly requires not only a die piece movable in the axial direction of the resultant fan housing but also a die piece movable in a direction perpendicular to the axial direction, in order to open the molding die assembly and allow removal of the resultant fan housing from the molding die assembly. Thus, the configuration of the molding die assembly becomes complicated. This prevents reduction in the manufacturing cost of the fan including that fan housing and a cooling apparatus in which the fan is attached to a heat sink, and also prevents improvement of manufacturing efficiency such as manufacturing speed.
In order to form the catch projection by using axially movable die pieces only, it is necessary for the die pieces to include an elongated pin-shaped portion for forming the axially upper surface of the catch projection. In this case, a hole through which the pin-shaped portion passes is inevitably formed in a portion of the resultant fan housing or holding arm located axially above the catch projection. The die piece having the pin-shaped portion can be easily broken and therefore the die life is short. In addition, the resultant fan housing has a drawback that the strength of a base portion of the holding arm is low due to the hole.